Electrical control means



July 10, 1962 MILTON ETAL. 3,043,937

ELECTRICAL CONTROL MEANS Filed July 28, 1959 INVENTORS Leonard Milron BY John S. Lory AT TO WNEY United States 3,043,937 ELECTRICAL CONTROL MEANS Leonard Milton, Lake Success, and John S. Lory, Syosset, N.Y., assignors to The Filtron Company, Inc. Filed July 28, 1959, Ser. No. 830,076 4 Claims. (Cl. 200-142) atet devices employing fusible links cannot provide reproducible results within narrow tolerances. In other instances, the thermal control devices are incorporated in equipment that imposes serious requirements on the size and weight of the devices. In airborne equipment, for instance, it is required that the control element be both light and compact and at the same time operate reliably at precise temperatures. Unfortunately, most proposed devices are usually large, complex and expensive. Often, in spite of their bulk and complexity, the precision of their temperature sensitivity is too coarse and not easily reproducible.

It is accordingly, a general object of the invention to provide an improved thermal circuit breaker.

It is another object of the invention to provide an improved thermal circuit breaker which is operative over a wide range of ambient temperatures and which is sensitive to within one percent of the rated temperature.

It is a further object of the invention to provide a thermal circuit breaker which is inexpensive, light in weight and of small volume.

Briefly, in accordance with the invention, a thermal circuit breaker is provided which includes a pair of electrical terminals extending in parallel spaced relation inwardly through the end wall of a housing. Within the housing is a movable spring-like contacting member that is in electrical contact with the electrical terminals. A pellet of a material which softens at a predetermined temperature is disposed between the spring-like contacting member and another end wall of the housing to maintain the spring-like contacting member in electrical contact with at least one of the electrical terminals.

Other objects, features and advantages of the invention will be evident from the following detailed description when read in connection with the accompanying drawing wherein:

FIGURE 1 is a perspective view of a thermal circuit breaker in accordance with an embodiment of the invention;

FIGURE 2 is a sectional view of the thermal circuit breaker of FIGURE 1 taken along the line 2-2;

FIGURE 3 is a top view of a disk spring contacting member incorporated in the thermal circuit breaker of FIGURE 1;

FIGURE 4 is a sectional view of a thermal circuit breaker in the closed position in accordance with another embodiment of the invention; and

FIGURE 5 is a sectional view of the thermal circuit breaker of FIGURE 4 in the open position.

Referring to FIGURES 1-3, there is shown a thermal circuit breaker :10 which comprises a housing 12 having first and second end wall members 18 and 20 at opposite ends of a cylindrical side Wall member 19. End wall member 18 is of insulative material. End wall 20 laterice ally extends beyond side wall member 19 to serve as a mounting bracket for the thermal circuit breaker 10. Extending through end wall member 18 are a pair of electrical terminals 14 and 16 which have flat ends 24 and 25 (FIG. 2). Electrical terminals 14 and 16 extend inwardly wi'thin housing 12 in substantially parallel spaced relationship to substantially the same depth. Disposed within housing 12 is a spring-like contacting member or disc spring 22 of a conductive material. Disc spring 22 has a cut 29 (FIG. 3) in its central region to provide a resilient tab 30. Disc spring 22 is freely movable in housing 12, but is initially positioned against the ends 24 and 25 of electrical terminals 14 and 16.

A pellet 26 of a rigid non-conducting material which softens at a predetermined temperature is disposed in a cup-shaped member 28. Cup-shaped member 28 is fixed to the inner surf-ace of end wall member 20. With pellet 26 in cup-shaped member 28 and disc spring 22 against the ends 24 and 25 of electrical terminals 14 and 16, pellet 2d exerts pressure against tab 30 to maintain disc spring 22 against the ends 24 and 25. There is, therefore, a continuous circuit between electrical terminals l4 and 16. However, when theambient temperature reaches the predetermined softening point of the pellet 26 the disc spring 22 falls away from at least one of the ends 24 and 25 to open the circuit between electrical terminals 14 and 16.

While in many applications the operation of thermal circuit breaker 10' suffices to indicate that the ambient temperature has reached the critical predetermined value, there are other applications which require even more reliable operation. To satisfy this more stringent requirement, the thermal circuit breaker 10' of FIGURES 4 and 5 may advantageously be employed. Since the thermal circuit breaker 10' is similar in many respects to the thermal circuit breaker 10 of FIGURES l and 2, primed reference characters are employed for like elements.

In particular, thermal circuit breaker 10 comprises the housing 12' having side wall members 19' with end wall members 18 and 20. Extending inwardly through end wall member 18' of insulative material are electrical terminals 14' and 16 in parallel spaced relationship. Disc spring 22' has one point fixed by rivet 32 to the end 24' of electrical terminal 14.

The diametrally opposite point 23' of disc spring 22 is opposite the end 25' of electrical terminal 16. Disc spring 22' is biased sothat point 23' will move away from end 25' of electrical terminal 16. Cup shaped member 28' fixed to end wall 20' accommodates one end of pellet 26'. The other end of pellet 26' presses against tab 30' of disc spring 22' to initially maintain point 23' in contact with the end 25 of electrical terminal 16 as shown in FIGURE 4. Therefore, there is a closed circuit between electrical terminals 14 and 16'. However, when the ambient temperature reaches the predetermined temperature at which pellet 26' softens, point 23' of disc spring 22' moves away from end 25 of electrical terminal 16 as shown in FIGURE 5. The circuit between electrical terminals 14' and 16' is accordingly opened.

There has thus been shown improved thermal circuit breakers which, by the use of a pellet which softens at a predetermined temperature, controls the contacting of a disc spring against at least one of a pair of electrical terminals to provide a simple, inexpensive and compact means for controlling the flow of electrical energy to utilization devices in a surrounding where the ambient temperature is critical.

This application is a continuation-in-part of application Serial No. 763,521, filed September 26, l958, now Patent No. 2,955,179.

speaesv 3 While only two embodiments of the invention have been shown and described in detail, there will now be obvious to those skilled in the art many modifications and variations which satisfy some or all of the objects of the invention and to which accrue many of its advantages, but which do not depart from the spirit of the invention as defined in the following claims.

What is claimed is:

1. A thermal circuit breaker comprising a cylindrical housing;

an insulative closure at one end of said housing;

a pair of electrical terminals supported on said closure in diametrically spaced relation, said terminal extending outwardly through said closure to provide external terminal tabs for connection to an external circuit, and extending inwardly to present front end surfaces to serve as contacting surfaces for the terminals;

a movable bridging contact member for engaging the two front end surfaces, said bridging contact member consisting of a relatively flat resilient disc having a central portion formed as a tab to have a limited amount of freedom for relative movement axially to thereby impress a resilient stress on the border portion of the disc to cause said border portion to engage said two front end surfaces of the two terminals; and a pellet of material which softens at a predetermined temperature and disposed to press against said tab to maintain said disc border portion in engagement with said two .front end surfaces of the two terminals below said predetermined temperature, and serving, upon softening above said predetermined temperature, to relieve the pressure tab, whereby the tab may function as a lever to stress the disc to impart movement to the free region of the border diametrically opposite to the restrained portion of the disc.

4. A thermal circuit breaker, as in claim 3, in which the housing is provided with an end closure and is further provided with a radially extending bracket for selectively positioning and anchoring the circuit breaker.

References Cited in the file of this patent UNITED STATES PATENTS 1,108,753 Herbeck Aug. 25, 1914 1,132,419 Ammons Mar. 16, 1915 1,852,312 Knight Apr. 5, 1932 1,986,507 Knight Jan. 1, 1935 2,085,379 Metzgar June 29, 1937 2,749,409 Kay June 5, 1956 2,955,179 Milton et al. Oct. 4, 1960 FOREIGN PATENTS 48,404 Sweden Jan. 19, 1921 

